Ok, i have a s5 streetported vert.
mods or intake exhaust ported TB/removed 2ndary throttle plates, and some other various things along with an untuned, but "setup" safc2

My idle has surged ever since i got it back from the auto-manual swap(although it did improve some from disconnecting the auto tranny computer.
I know my TPS is working perfectly, because the SAFC displays the throttle perfectly in sync with my foot.
And today I grounded the trailing and lealding coils, and the fuel injection harness with 14ga wire. When i first started it, it idled smooth at 1500 for a few seconds, then died (probably due to TB mod). but then i started it up again, it still surged. 1k-1.5k.
The rpm graph display on the SAfc looks like a ripply line cuz of the surging pls help

 

First the SAFC should be reading the wide range TPS, which seems to be working.

The short range TPS tells the ECU when you're at closed throttle.
If anything (vac leak, or just a high idle setting) pushes warmed up idle RPM over 1500, the ECU will fuel cut till it falls back down. (zoom zoom zoom)

Any check codes?

 

did you plug the vac line going to the auto transmission? there's a little stub near the brake booster vac connection that sticks out. It's 3/8'ths I think... plug it and your surging will stop.

edit: I am almost positive this is your problem as it was my problem too... almost exactly.

 

I regrounded the specified grounds with brand new 10ga wire, and it started up and held a stead 1500 idle, then died, then started jumping again the second time i started it. what in the world.

 

um... did you check out what I said? I had the SAME problem till I capped off that line!

 

wtf? sorry i donno why this posted when it did because i posted this WAY earlier when nobody else posted yet.
and nonameo ill check into this now

 

BTW where is the brake booster vac connection? (sorry)

 

btw thanks for all the replies.

 

trace the FAT hose that comes off of the booster and goes to the left(from your perspective looking over the car, i.e. the brake booster's right)

its about 4 inches TOWARDS the transmission... its a nub you can't miss it! it may be broken off, not sure.

edit: I'd take pics but my dad drove my car to put some miles on it.

 

check your idle adjust screw, like Sureshot said, you may have it tweaked above that 1500 rpm point, and the ECU is killing it...tweak it clockwise about 1/2 turn, that should drop it a couple hundred rpm...

 

is the idle screw near the BAC? sorry i dont quite know everything yet

 

On an S4 n/a it's on top of the throttle body, beneath a black cap...I think the turbo's were in a slightly different location....

 

i have an s5 na

 

its the same for S4/S5 NAs, there is a little black rubber cap on the top of the intake manifold, use a flat head screw driver to tweek it down (counter clockwise)

 

... does someone have a camera so they can take a pic of that vac line for him? I swear this is his problem...

 

i screwed it all the way in and that lowered the idle some. Now, my car idles great, thanks everybody